Problems Set #2-Solns
Problems Set #2-Solns 1. Which of the following is not the correct chemical formula for the compound named? a. hydrocyanic acid HCN(aq) b. calcium sulfate CaSO4 c. beryllium oxide BeO d. nickel(II) peroxide Ni2O e. ammonium chromate (NH4)2CrO4 ANSWER:
d. nickel(II) peroxide
2. The correct name for FeO is a. iron oxide b. iron(II) oxide c. iron(III) oxide d. iron monoxide e. iron(I) oxide ANSWER:
b.
iron(II) oxide
3. Titanium(IV) oxide has the formula a. Ti4O b. TiO4 c. Ti(IV)O d. TiO2 e. Ti4O2 ANSWER:
d. TiO2
4. The formula for calcium hydrogen sulfate is a. Ca(SO4)2 b. CaS2 c. Ca(HSO4)2 d. Ca2HSO4 e. Ca2S ANSWER:
c.
Ca(HSO4) 2
5. The name of the compound NH4ClO4 is a. ammonium perchlorate b. ammonium chlorite c. ammonium chlorate d. ammonium hypochlorate e. ammonium chloride
ANSWER:
a.
ammonium perchlorate
6. What is the name for HPO42 ? a. phosphate ion b. phosphite ion c. hydrogen phosphate ion d. hydrogen phosphite ion e. hydrogen phosphorus oxide ion ANSWER:
c.
hydrogen phosphate ion
7. The substance ClO3 is best described as a. a molecule b. a polyatomic ion c. a polyatomic molecule d. a mixture ANSWER:
b.
a polyatomic ion
8. The formula for the compound formed from the polyatomic ions NH4+ and PO43 is a. NH4(PO4)3 b. NH4PO4 c. (NH4)3PO4 d. (NH4)2(PO4)2 ANSWER: c. (NH4)3PO4 9. Which of the following is named incorrectly? What should its name be? a. FeSO4; iron(II) sulfate b. Sn3(PO4)4; tin(IV) phosphate c. K3P; potassium phosphide d. Fe(OH)2; iron(III) hydroxide e. All are correct. ANSWER: 10.
d. This answer is incorrect. It should be Fe(OH)2; iron(II) hydroxide.
Aluminum oxide solid reacts with gaseous carbon monoxide to produce aluminum metal and carbon dioxide gas. Write the balanced equation for this reaction. ANSWER: Al2O3(s) + 3CO(g) 2Al(s) + 3CO2(g)
11.
Sodium metal reacts with water to produce aqueous sodium hydroxide and hydrogen gas. Write the balanced equation for this reaction. ANSWER: 2Na(g) + 2H2O(l) 2NaOH(aq) + H2(g)
12. When the following equations are balanced using the smallest possible integers, what is the number in front of the bold-underlined substance in each case? C3H8(g) + O2(g) CO2(g) + H2O(g) a. b. c. d. e.
2 3 4 5 6
ANSWER:
d. 5
13. H3PO4(aq) + Ca(OH)2(aq) Ca3(PO4)2(aq) + H2O(l) _____ a. 2 b. 3 c. 4 d. 5 e. 6 ANSWER:
e.
6
14. Na(s) + H2O(l) NaOH(aq) + H2(g) _____ a. 2 b. 3 c. 4 d. 5 e. 6 ANSWER:
a.
2
15. MgO(s) Mg(s) + O2(g) _____ a. 2 b. 3 c. 4 d. 5 e. 6 ANSWER: a. 2 16. Al(s) + O2(g) Al2O3(s) ____ a. 2 b. 3 c. 4 d. 5 e. 6 ANSWER: b. 3 17. The sum of the coefficients when the following equation is balanced is BaSO4 + K3PO4 Ba3(PO4)2 + K2SO4 a. 4
b. c. d. e.
7 8 9 11
ANSWER:
d. 9
18. Which of the following statements concerning balancing equations is false? a. There must always be a coefficient of 1 in an equation balanced in standard form. b. The ratio of coefficients is much more meaningful than an individual coefficient in a balanced equation. c. The total number of atoms must be the same on the reactants side and the product side of the balanced equation. d. When there are two products, the order in which they are written does not matter. e. At least two of these statements (a-d) are false. ANSWER:
a.
1
19. Consider the reaction represented by the unbalanced equation NH3 + O2 NO + H2O. For every 1.00 mol of NH3 that reacts, _____ mol of O2 is required. a. 1 b. 1.25 c. 4.00 d. 5.00 e. none of these ANSWER:
b.
1.25
20. Consider a reaction given by the equation aA + bB cC + dD. In this equation A, B, C, D represent chemicals, and a, b, c, d represent coefficients in the balanced equation. For a given reaction, how many values are there for the quantity “c/d”? a. 1 b. 2 c. 3 d. 4 e. an infinite number ANSWER:
a.
1
21. Choose the response that best answers the question “Why do we not change subscripts when balancing a chemical equation?” a. There’s no real reason not to, it’s just something that is not done. b. We never change subscripts because atoms are neither created nor destroyed. This is part of the law of conservation of matter. c. It’s fine to do once in awhile, but don’t make a habit of it. d. We can change subscripts. We can’t change coefficients. e. Compounds composed of the same elements and having different subscripts are different substances. ANSWER:
e.
Compounds composed of the same elements and having different subscripts are different substances.
22.
Balance the equation NaBH4 + BF3 NaBF4 + B2H6 ANSWER: 3NaBH4 + 4BF3 3NaBF4 + 2B2H6
23. Balance the equation MgCl2 + K3PO4 Mg3(PO4)2 + KCl ANSWER: 3MgCl2 + 2K3PO4 Mg3(PO4)2 + 6KCl 24. Balance the equation C6H14 + O2 CO2 + H2O ANSWER: 2C6H14 + 19O2 12CO2 + 14H2O 25. Balance the equation As2O3(s) + Ca(OH)2(aq) Ca3(AsO4)2(s) + H2O(l) ANSWER: As2O3(s) + 3Ca(OH)2(aq) Ca3(AsO4)2(s) + 3H2O(l) 26. Balance the equation KClO3(s) KCl(s) + O2(g) ANSWER: 2KClO3(s) 2KCl(s) + 3O2(g) 27. When table sugar is burned in air, carbon dioxide and water vapor are products as shown by the following unbalanced chemical equation C12H22O11(s) + O2(g) CO2(g) + H2O(g) How many moles of oxygen are required to react completely with 1.0 mol of sugar? a. 12 b. 17.5 c. 24 d. 35 e. none of these ANSWER:
a.
12
28. When ethane (C2H6) is reacted with oxygen in the air, the products are carbon dioxide and water. This process requires _____ mol of oxygen for every one mole of ethane. a. 1 b. 2.5 c. 3.5 d. 7 e. none of these ANSWER:
c.
3.5
29. Write and balance the equation showing the reaction between calcium metal and water to form aqueous calcium hydroxide and hydrogen gas.
ANSWER: Ca(s) +2H2O(l) Ca(OH)2(aq) +H2(g) 30. Write and balance the equation showing the reaction between iron(III) oxide and carbon monoxide to form iron(II) oxide and carbon dioxide. ANSWER: Fe2O3(s) +CO(g) 2FeO(s) +CO2(s) 31. Write and balance the equation showing the reaction between copper metal and aqueous sulfuric acid to form aqueous copper(II) sulfate, sulfur dioxide gas, and water. ANSWER: Cu(s) +2H2SO4(aq) CuSO4(aq) + SO2(g) + 2H2O(l)
When the following equations are balanced using the smallest possible integers, what is the number in front of the underlined substance in each case? 32. Sb(s) + O2 (g) Sb2O5(s) _____ a. 1 b. 2 c. 4 d. 6 e. 12 ANSWER:
c.
4
33. C4H10(g) + O2(g) CO2(g) + H2O(g) _____ a. 2 b. 4 c. 6 d. 8 e. 10 ANSWER:
d. 8
34. CH3OH(l) + O2(g) CO2(g) + H2O(g) ______ a. 1 b. 2 c. 4 d. 6 e. 12 35. Balance the equation Pb(NO3)2(aq) + K2CrO4(aq) PbCrO4(s) + KNO3(aq) ANSWER: Pb(NO3)2(aq) + K2CrO4(aq) PbCrO4(s) + 2KNO3(aq) 36. Balance the equation
(NH4)2Cr2O7(s) N2(g) + H2O(g) + Cr2O3(s) ANSWER: (NH4)2Cr2O7(s) N2(g) + 4H2O(g) + Cr2O3(s) 37. When the equation Si(s) + HF(aq) SiF4(g) + H2(g) is balanced, what is the coefficient for HF? a. 0 b. 1 c. 2 d. 3 e. 4 ANSWER:
e.
4
38. Balance the equation Zn(s) + H3PO4(aq) Zn3(PO4)2(s) + H2(g) ANSWER: 3Zn(s) + 2H3PO4(aq) Zn3(PO4)2(s) + 3H2(g) 39. Calculate the molar mass of a sample if a single molecule weighs 5.34 10 2 3 g.
a. b. c. d. e.
1.13 10 4 6 g/mol 12.0 g/mol 5.34 10 2 3 g/mol 32.2 g/mol none of these
ANSWER:
d. 32.2 g/mol
40. What is the mass of one atom of copper in grams? a. 63.5 g b. 52.0 g c. 58.9 g d. 65.4 g e. 1.06 10 2 2 g ANSWER:
e.
1.06 10 2 2 g
41. How many moles of Ca atoms are in 801 g Ca? a. 4.99 10 2 mol b. 20.0 mol c. 40.0 mol d. 1.60 10 3 mol e. 801 mol ANSWER: b. 20.0 mol 42. What is the mass of 2.00 moles of Ca(OH)2? a. 74.1 g b. 56 g c. 122.5 g d. 222.4 g
e.
148.2 g
ANSWER:
e.
148.2 g
43. A 20.0-g sample of Ca contains how many calcium atoms? a. 20.0 atoms b. 40.1 atoms c. 0.500 atoms d. 6.02 10 2 3 atoms e.
3.0 10 2 3 atoms
ANSWER: e. 3.0 10 2 3 atoms 44. The molar mass of calcium phosphate is a. 324.99 g/mol b. 310.18 g/mol c. 175.13 g/mol d. 135.05 g/mol e. none of these ANSWER:
b.
310.18 g/mol
45. What is the mass of 1.48 mol of potassium sulfide? a. 105 g b. 153 g c. 163 g d. 221 g e. none of these ANSWER: c. 163 g 46. Which of the following contains the smallest number of molecules? a. 5.0 g CO2 b. 5.0 g O2 c. 5.0 g N2 d. 5.0 g H2O ANSWER:
a.
5.0 g CO2
47. Which of the following has the largest percent by mass of carbon? a. CaCO3 b. CO2 c. CH4 d. NaHCO3 ANSWER: c. CH4 48. Which of the following has the highest mass percentage of nitrogen? a. NH3 b. N2H4 c. HNO3
d. NH4NO3 e. NO ANSWER:
b.
N2H4
49. Which of the following has the empirical formula CH2? a. C2H6 b. H2CO3 c. C6H6 d. C6H12 e. C2H4O ANSWER: 50.
d. C6H12
Choose the pair of compounds with the same empirical formula. a. C2H2 and C6H6 b. NaHCO3 and Na2CO3 c. K2CrO4 and K2Cr2O7 d. H2O and H2O2 ANSWER:
a.
C2H2 and C6H6
51. A sample of metal weighing 2.51 g is combined with oxygen; the metal oxide weighs 3.01 g. The mass percent of oxygen in the compound is a. 19.9% b. 16.6% c. 83.4% d. 50.0% e. cannot be determined from information given ANSWER:
b.
16.6%
52. Calculate the molecular formula of a compound with the empirical formula CH 2O and a molar mass of 150 g/mol. a. C2H4O2 b. C3H6O3 c. C4H8O4 d. C5H10O5 e. C6H12O6 ANSWER:
d. C5H10O5
d. nickel(II) peroxide
2. The correct name for FeO is a. iron oxide b. iron(II) oxide c. iron(III) oxide d. iron monoxide e. iron(I) oxide ANSWER:
b.
iron(II) oxide
3. Titanium(IV) oxide has the formula a. Ti4O b. TiO4 c. Ti(IV)O d. TiO2 e. Ti4O2 ANSWER:
d. TiO2
4. The formula for calcium hydrogen sulfate is a. Ca(SO4)2 b. CaS2 c. Ca(HSO4)2 d. Ca2HSO4 e. Ca2S ANSWER:
c.
Ca(HSO4) 2
5. The name of the compound NH4ClO4 is a. ammonium perchlorate b. ammonium chlorite c. ammonium chlorate d. ammonium hypochlorate e. ammonium chloride
ANSWER:
a.
ammonium perchlorate
6. What is the name for HPO42 ? a. phosphate ion b. phosphite ion c. hydrogen phosphate ion d. hydrogen phosphite ion e. hydrogen phosphorus oxide ion ANSWER:
c.
hydrogen phosphate ion
7. The substance ClO3 is best described as a. a molecule b. a polyatomic ion c. a polyatomic molecule d. a mixture ANSWER:
b.
a polyatomic ion
8. The formula for the compound formed from the polyatomic ions NH4+ and PO43 is a. NH4(PO4)3 b. NH4PO4 c. (NH4)3PO4 d. (NH4)2(PO4)2 ANSWER: c. (NH4)3PO4 9. Which of the following is named incorrectly? What should its name be? a. FeSO4; iron(II) sulfate b. Sn3(PO4)4; tin(IV) phosphate c. K3P; potassium phosphide d. Fe(OH)2; iron(III) hydroxide e. All are correct. ANSWER: 10.
d. This answer is incorrect. It should be Fe(OH)2; iron(II) hydroxide.
Aluminum oxide solid reacts with gaseous carbon monoxide to produce aluminum metal and carbon dioxide gas. Write the balanced equation for this reaction. ANSWER: Al2O3(s) + 3CO(g) 2Al(s) + 3CO2(g)
11.
Sodium metal reacts with water to produce aqueous sodium hydroxide and hydrogen gas. Write the balanced equation for this reaction. ANSWER: 2Na(g) + 2H2O(l) 2NaOH(aq) + H2(g)
12. When the following equations are balanced using the smallest possible integers, what is the number in front of the bold-underlined substance in each case? C3H8(g) + O2(g) CO2(g) + H2O(g) a. b. c. d. e.
2 3 4 5 6
ANSWER:
d. 5
13. H3PO4(aq) + Ca(OH)2(aq) Ca3(PO4)2(aq) + H2O(l) _____ a. 2 b. 3 c. 4 d. 5 e. 6 ANSWER:
e.
6
14. Na(s) + H2O(l) NaOH(aq) + H2(g) _____ a. 2 b. 3 c. 4 d. 5 e. 6 ANSWER:
a.
2
15. MgO(s) Mg(s) + O2(g) _____ a. 2 b. 3 c. 4 d. 5 e. 6 ANSWER: a. 2 16. Al(s) + O2(g) Al2O3(s) ____ a. 2 b. 3 c. 4 d. 5 e. 6 ANSWER: b. 3 17. The sum of the coefficients when the following equation is balanced is BaSO4 + K3PO4 Ba3(PO4)2 + K2SO4 a. 4
b. c. d. e.
7 8 9 11
ANSWER:
d. 9
18. Which of the following statements concerning balancing equations is false? a. There must always be a coefficient of 1 in an equation balanced in standard form. b. The ratio of coefficients is much more meaningful than an individual coefficient in a balanced equation. c. The total number of atoms must be the same on the reactants side and the product side of the balanced equation. d. When there are two products, the order in which they are written does not matter. e. At least two of these statements (a-d) are false. ANSWER:
a.
1
19. Consider the reaction represented by the unbalanced equation NH3 + O2 NO + H2O. For every 1.00 mol of NH3 that reacts, _____ mol of O2 is required. a. 1 b. 1.25 c. 4.00 d. 5.00 e. none of these ANSWER:
b.
1.25
20. Consider a reaction given by the equation aA + bB cC + dD. In this equation A, B, C, D represent chemicals, and a, b, c, d represent coefficients in the balanced equation. For a given reaction, how many values are there for the quantity “c/d”? a. 1 b. 2 c. 3 d. 4 e. an infinite number ANSWER:
a.
1
21. Choose the response that best answers the question “Why do we not change subscripts when balancing a chemical equation?” a. There’s no real reason not to, it’s just something that is not done. b. We never change subscripts because atoms are neither created nor destroyed. This is part of the law of conservation of matter. c. It’s fine to do once in awhile, but don’t make a habit of it. d. We can change subscripts. We can’t change coefficients. e. Compounds composed of the same elements and having different subscripts are different substances. ANSWER:
e.
Compounds composed of the same elements and having different subscripts are different substances.
22.
Balance the equation NaBH4 + BF3 NaBF4 + B2H6 ANSWER: 3NaBH4 + 4BF3 3NaBF4 + 2B2H6
23. Balance the equation MgCl2 + K3PO4 Mg3(PO4)2 + KCl ANSWER: 3MgCl2 + 2K3PO4 Mg3(PO4)2 + 6KCl 24. Balance the equation C6H14 + O2 CO2 + H2O ANSWER: 2C6H14 + 19O2 12CO2 + 14H2O 25. Balance the equation As2O3(s) + Ca(OH)2(aq) Ca3(AsO4)2(s) + H2O(l) ANSWER: As2O3(s) + 3Ca(OH)2(aq) Ca3(AsO4)2(s) + 3H2O(l) 26. Balance the equation KClO3(s) KCl(s) + O2(g) ANSWER: 2KClO3(s) 2KCl(s) + 3O2(g) 27. When table sugar is burned in air, carbon dioxide and water vapor are products as shown by the following unbalanced chemical equation C12H22O11(s) + O2(g) CO2(g) + H2O(g) How many moles of oxygen are required to react completely with 1.0 mol of sugar? a. 12 b. 17.5 c. 24 d. 35 e. none of these ANSWER:
a.
12
28. When ethane (C2H6) is reacted with oxygen in the air, the products are carbon dioxide and water. This process requires _____ mol of oxygen for every one mole of ethane. a. 1 b. 2.5 c. 3.5 d. 7 e. none of these ANSWER:
c.
3.5
29. Write and balance the equation showing the reaction between calcium metal and water to form aqueous calcium hydroxide and hydrogen gas.
ANSWER: Ca(s) +2H2O(l) Ca(OH)2(aq) +H2(g) 30. Write and balance the equation showing the reaction between iron(III) oxide and carbon monoxide to form iron(II) oxide and carbon dioxide. ANSWER: Fe2O3(s) +CO(g) 2FeO(s) +CO2(s) 31. Write and balance the equation showing the reaction between copper metal and aqueous sulfuric acid to form aqueous copper(II) sulfate, sulfur dioxide gas, and water. ANSWER: Cu(s) +2H2SO4(aq) CuSO4(aq) + SO2(g) + 2H2O(l)
When the following equations are balanced using the smallest possible integers, what is the number in front of the underlined substance in each case? 32. Sb(s) + O2 (g) Sb2O5(s) _____ a. 1 b. 2 c. 4 d. 6 e. 12 ANSWER:
c.
4
33. C4H10(g) + O2(g) CO2(g) + H2O(g) _____ a. 2 b. 4 c. 6 d. 8 e. 10 ANSWER:
d. 8
34. CH3OH(l) + O2(g) CO2(g) + H2O(g) ______ a. 1 b. 2 c. 4 d. 6 e. 12 35. Balance the equation Pb(NO3)2(aq) + K2CrO4(aq) PbCrO4(s) + KNO3(aq) ANSWER: Pb(NO3)2(aq) + K2CrO4(aq) PbCrO4(s) + 2KNO3(aq) 36. Balance the equation
(NH4)2Cr2O7(s) N2(g) + H2O(g) + Cr2O3(s) ANSWER: (NH4)2Cr2O7(s) N2(g) + 4H2O(g) + Cr2O3(s) 37. When the equation Si(s) + HF(aq) SiF4(g) + H2(g) is balanced, what is the coefficient for HF? a. 0 b. 1 c. 2 d. 3 e. 4 ANSWER:
e.
4
38. Balance the equation Zn(s) + H3PO4(aq) Zn3(PO4)2(s) + H2(g) ANSWER: 3Zn(s) + 2H3PO4(aq) Zn3(PO4)2(s) + 3H2(g) 39. Calculate the molar mass of a sample if a single molecule weighs 5.34 10 2 3 g.
a. b. c. d. e.
1.13 10 4 6 g/mol 12.0 g/mol 5.34 10 2 3 g/mol 32.2 g/mol none of these
ANSWER:
d. 32.2 g/mol
40. What is the mass of one atom of copper in grams? a. 63.5 g b. 52.0 g c. 58.9 g d. 65.4 g e. 1.06 10 2 2 g ANSWER:
e.
1.06 10 2 2 g
41. How many moles of Ca atoms are in 801 g Ca? a. 4.99 10 2 mol b. 20.0 mol c. 40.0 mol d. 1.60 10 3 mol e. 801 mol ANSWER: b. 20.0 mol 42. What is the mass of 2.00 moles of Ca(OH)2? a. 74.1 g b. 56 g c. 122.5 g d. 222.4 g
e.
148.2 g
ANSWER:
e.
148.2 g
43. A 20.0-g sample of Ca contains how many calcium atoms? a. 20.0 atoms b. 40.1 atoms c. 0.500 atoms d. 6.02 10 2 3 atoms e.
3.0 10 2 3 atoms
ANSWER: e. 3.0 10 2 3 atoms 44. The molar mass of calcium phosphate is a. 324.99 g/mol b. 310.18 g/mol c. 175.13 g/mol d. 135.05 g/mol e. none of these ANSWER:
b.
310.18 g/mol
45. What is the mass of 1.48 mol of potassium sulfide? a. 105 g b. 153 g c. 163 g d. 221 g e. none of these ANSWER: c. 163 g 46. Which of the following contains the smallest number of molecules? a. 5.0 g CO2 b. 5.0 g O2 c. 5.0 g N2 d. 5.0 g H2O ANSWER:
a.
5.0 g CO2
47. Which of the following has the largest percent by mass of carbon? a. CaCO3 b. CO2 c. CH4 d. NaHCO3 ANSWER: c. CH4 48. Which of the following has the highest mass percentage of nitrogen? a. NH3 b. N2H4 c. HNO3
d. NH4NO3 e. NO ANSWER:
b.
N2H4
49. Which of the following has the empirical formula CH2? a. C2H6 b. H2CO3 c. C6H6 d. C6H12 e. C2H4O ANSWER: 50.
d. C6H12
Choose the pair of compounds with the same empirical formula. a. C2H2 and C6H6 b. NaHCO3 and Na2CO3 c. K2CrO4 and K2Cr2O7 d. H2O and H2O2 ANSWER:
a.
C2H2 and C6H6
51. A sample of metal weighing 2.51 g is combined with oxygen; the metal oxide weighs 3.01 g. The mass percent of oxygen in the compound is a. 19.9% b. 16.6% c. 83.4% d. 50.0% e. cannot be determined from information given ANSWER:
b.
16.6%
52. Calculate the molecular formula of a compound with the empirical formula CH 2O and a molar mass of 150 g/mol. a. C2H4O2 b. C3H6O3 c. C4H8O4 d. C5H10O5 e. C6H12O6 ANSWER:
d. C5H10O5
